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85 Gyro S carburetor issue
Posted: Thu Jul 27, 2023 11:25 pm
by motormike
Have owned and ridden my Gyro S for 13 years.
Last time the carb was cleaned has been several years.
The issue has been present the entire life of this bike in my ownership.
When approaching top speed, it does well on the flat, but going downhill,
the engine starts to 4-stroke, and lose power. Once the bike is back on the flat,
it pulls normally at WOT. On the downhill, at top speed,
if I roll off to find a sweet spot with the throttle,
the bike will run normal without the 4-stroking. Very tedious throttle movement is required.
It CANNOT handle WOT on a downhill. Just starts backing up.
I've always thought that the main jet is too lean, thinking logically about it.
But, I've never tried any smaller or larger jets because I don't know where I'd find compatible jets.
Can't justify doing anything with my only jet..don't want to ruin my only one.
Any help and opinion about the diagnosis is welcomed....motor... 
Re: 85 Gyro S carburetor issue
Posted: Fri Jul 28, 2023 7:45 am
by vintagegarage
Mine does the same thing, and I do the same thing.. i.e. I roll off the throttle a bit when going downhill. Fortunately, I don't have many hills where I live. I have a complete jet kit, but haven't tried changing main jets or moving the needle clip, i just live with it.
Re: 85 Gyro S carburetor issue
Posted: Fri Jul 28, 2023 11:28 am
by motormike
vintagegarage wrote: ↑Fri Jul 28, 2023 7:45 am
I have a complete jet kit,
Can you direct me to a kit ?
Re: 85 Gyro S carburetor issue
Posted: Fri Jul 28, 2023 7:22 pm
by vintagegarage
Mike, That is a tough one. I started with this one, just to get the box:
https://www.ebay.com/itm/223270638716
If I am correct and your gyro is stock, you have a #75 Main jet, so that kit will only give you one main jet that is leaner. Sprees use the same main jet, but they are #62 through #68 which would seem to be too lean for you. Every time I throw away a carb, I add the main jet from it to the original kit. I also order them one at a time to fill in the holes in the kit. For example, a #70 main jet is here:
https://www.treatland.tv/honda-EXPRESS- ... 1&CartID=0
use the pulldown menu and select 70, and so on. If all you want is a 70, 72, 74 to experiment with, order the three from Treatland and forget about the kit unless you want the box. If you want to test richer, then the kit is a good starting point.
Re: 85 Gyro S carburetor issue
Posted: Thu Aug 03, 2023 5:02 pm
by motormike
Very good info vintage 
I'm going for the Naraku kit.
Re: 85 Gyro S carburetor issue
Posted: Fri Dec 22, 2023 5:40 pm
by harleyracer59
hey mike. check your float level... too high will caue your exact issue.. lower it a 1/2 a mmm and see if it fixes your problem i dont think you have a jetting issue
Re: 85 Gyro S carburetor issue
Posted: Sat Dec 23, 2023 3:05 pm
by motormike
harleyracer59 wrote: ↑Fri Dec 22, 2023 5:40 pm
hey mike. check your float level... too high will caue your exact issue.. lower it a 1/2 a mmm and see if it fixes your problem i dont think you have a jetting issue
Okay...good stuff HR59...and seems to make sense.
Will keep this in mind next March when I pull the Gyro out of storage.
Had a problem with left rear wheel this year, and went into storage unit in Nov.
Thank you sir....motor
Re: 85 Gyro S carburetor issue
Posted: Sat Jan 13, 2024 3:24 am
by harleyracer59
motormike wrote: ↑Sat Dec 23, 2023 3:05 pm
harleyracer59 wrote: ↑Fri Dec 22, 2023 5:40 pm
hey mike. check your float level... too high will caue your exact issue.. lower it a 1/2 a mmm and see if it fixes your problem i dont think you have a jetting issue
Okay...good stuff HR59...and seems to make sense.
Will keep this in mind next March when I pull the Gyro out of storage.
Had a problem with left rear wheel this year, and went into storage unit in Nov.
Thank you sir....motor
Left rear wheel is the coaster side. What was your issue? I have some spare parts and will help you any way I can. I owe you for those parts that helped me out a couple years ago.
Re: 85 Gyro S carburetor issue
Posted: Sat Jan 13, 2024 6:05 pm
by motormike
harleyracer59 wrote: ↑Sat Jan 13, 2024 3:24 am
Left rear wheel is the coaster side. What was your issue? I have some spare parts and will help you any way I can. I owe you for those parts that helped me out a couple years ago.
Exact problem not yet diagnosed. Noticed the wheel showing some wobble.
Wheel is bolted securely to the brake drum, but drum is NOT tight on the axle.
This happened maybe 3 years ago, and the problem that time was all the splines had stripped out of the brake drum.
That incident didn't DESTROY the axle splines, but it DID booger them up a tad.
I was able to remove the axle nut with some trouble, and install a spare brake drum.
It went on pretty good, but not as perfectly as new, but I put the axle nut on and impacted it until it stopped.
I knew at the moment that if it ever happened again, I was going to have some serious trouble ever getting it off again.
So, here I am again with apparently the same issue, judging from first impression.
Since it was late in the season, I just decided to shove it in storage and tackle it this Spring.
I DO have a spare brake hub, but if the axle is stripped, I don't know how that rascal is attached.
It promises to be a challenge, regardless of the issue. I'll post up when March gets here.
Thanks for your offer, may take you up on that....motor
Re: 85 Gyro S carburetor issue
Posted: Wed Jan 31, 2024 9:40 pm
by harleyracer59
motormike wrote: ↑Sat Jan 13, 2024 6:05 pm
harleyracer59 wrote: ↑Sat Jan 13, 2024 3:24 am
Left rear wheel is the coaster side. What was your issue? I have some spare parts and will help you any way I can. I owe you for those parts that helped me out a couple years ago.
Exact problem not yet diagnosed. Noticed the wheel showing some wobble.
Wheel is bolted securely to the brake drum, but drum is NOT tight on the axle.
This happened maybe 3 years ago, and the problem that time was all the splines had stripped out of the brake drum.
That incident didn't DESTROY the axle splines, but it DID booger them up a tad.
I was able to remove the axle nut with some trouble, and install a spare brake drum.
It went on pretty good, but not as perfectly as new, but I put the axle nut on and impacted it until it stopped.
I knew at the moment that if it ever happened again, I was going to have some serious trouble ever getting it off again.
So, here I am again with apparently the same issue, judging from first impression.
Since it was late in the season, I just decided to shove it in storage and tackle it this Spring.
I DO have a spare brake hub, but if the axle is stripped, I don't know how that rascal is attached.
It promises to be a challenge, regardless of the issue. I'll post up when March gets here.
Thanks for your offer, may take you up on that....motor
Here you go mike. 30$ and free shipping. Can’t beat that price for the whole left side, with axle and brake shoes. If you got an extra brake hub. You’re all set.
https://www.ebay.com/itm/325300634513?m ... media=COPY
Re: 85 Gyro S carburetor issue
Posted: Thu Feb 01, 2024 11:28 am
by motormike
Thanks HR59, but I see that part #'s do not match, and I can see obvious difference between 84 and 85.
Although the differences may not affect fit and function, so there's that. I see now how that axle is mounted to the cover, so your comment has been helpful in that regard. I may need to replace the cover, but I may not. Might be much simpler, at least I hope so..lol.
Re: 85 Gyro S carburetor issue
Posted: Fri Feb 02, 2024 11:34 pm
by harleyracer59
If I remember correctly. The axle just bolts into a bearing that’s pressed into case. Here’s am 85 piece and it’s cheaper. I’ve had a few gyros down to bare cases. That side cover just bolts onto the engine cases. You have to remove that cover to get the cooling fan off. And remove the flywheel and work on the stator and stuff.
https://www.ebay.com/itm/184689829458?m ... media=COPY
